In a flat panel display, notably a liquid crystal display and a plasma display, one where a semiconductor chip is mounted over a circuit substrate having flexibility (a flexible substrate; hereinafter, it is called a base film) has been widely used for a semiconductor device for driving them.
In general, as a semiconductor device for driving which achieves a high density for packaging semiconductor chips, there is a TCP (Tape Carrier Package) and, in particular, one where there is no device hole and where an inner lead connected with a bump electrode over the semiconductor chip makes contact with the base film, which is the substrate, is a COF (Chip On Film: hereinafter, it is called COF). On the other hand, a TCP in a narrow sense is used as a word to distinguish itself from a COF, in which there is a device hole formed by cutting the tape substrate and there is a connection between the inner lead existing at the device hole (it is called a flying lead) and the terminal of the semiconductor chip. Hereinafter, when it is only called TCP, it means this TCP in a narrow sense.
Since the COF has the aforementioned structure, it is different from the TCP and has no flying lead which is easily bent; it can make the lead thinner; it has features where the etching characteristics of the circuit interconnection layer is improved and a fine pitch process is easily applied. Therefore, in recent years this COF has been mainstream.
On the other hand, in a flat panel display for a wide screen television set, there is a concern that the reliability of the semiconductor device is impaired by heat produced from the semiconductor device for driving and that the display quality is impaired by propagation of the heat to the flat panel display.
Conventionally, as a means for heat dissipation of this COF, JP-A-2006-108356 and JP-A-2006-64939 disclose a technology where a metallic heat radiating body and heat radiating tape are attached over the rear surface of the base film.
Moreover, although it is not a COF, a conventional heat dissipation means will be described for reference purposes. As a technology for contacting a cooling material directly with the rear surface of the semiconductor chip, JP-A-2003-303928 discloses a technology where the rear surface of a semiconductor ship is covered with paint and a tape, and JP-A-Hei06 (1994)-310621 discloses a technology where a cooling body is attached over the rear surface of a semiconductor chip.
Next, there is a technology related to a change of the material and the structure of a surface protection film of a semiconductor element. In JP-A-2005-276943, a technology is disclosed in which a solder-resist coated as an insulation of the conventional circuit interconnection layer is replaced by a liquid ceramic; JP-A-Hei10(1998)-125834 discloses a technology for sealing a semiconductor element by using double resins; and JP-A-Hei08 (1996)-279567 and JP-A-Hei08 (1996)-279533 disclose a technology where a semiconductor element is covered with a metallic layer having a low melting-point.